In the patents mentioned above, the seating was supported by flexible members so as to enable it to rotate with respect to the chair frame, thereby enabling the user to vary his position from upright sitting to fully reclining sitting. A reclinable chair being more comfortable and healthier for its occupant.
Runners attached to the four corners of the seating board went through slots machined in the chair's frame whereby they attached to the ends of said flexible members. Each of the four slots where shaped like a circular sector, with the diameter of said sectors matching the distance between the front and the rear runners. Hence, the rotation of the seating was guided by the geometry of said slots. Expressly, the sliding of the runners over the edges of the slots controlled the motions of the seating.
Though the chairs having a suspended seating worked smoothly and effortlessly, the cumbersome mechanism and the aesthetic design constrains in the frame, needed to house said mechanism, were a big drawback. Another drawback was the impossibility to build an armless chair, since armrests were needed to house the mechanism, and used by the chair occupant to pull the seat forward from the reclined positions.
In the present invention—basically—the seat has plastic shoes or runners that slide over circular slots called here the raceways, that are attached to the frame. The sliding travel of the runners over the raceways defines the seat pivoting degree of rotation. Due to the nature of the sliding surfaces, all the motions are then smoothly and noiselessly attained.
But the most desirable characteristic of a non-powered reclinable seat should be its ability to rotate effortlessly over its whole arc of pivoting and to retain—also effortlessly—any attained seat position.
In the present invention this is achieved by the combination of two features:    a) By placing the center of rotation of the seat to the rear of the assumed center of gravity of the seat-occupant entirety, whenever the occupant tilts the seat back by pushing with his legs, it rises the center of gravity, hence, increasing the gravitational potential energy of the entirety. Thus, to bring the seat forward, the occupant just let go—intuitively—with his legs and gravity will bring the seat forward, effortlessly, up to its fully upright position, if wanted. And,    b) By making the resistance to rotate the seat proportional to the occupant weight, we achieve a reclining chair that is friendly to everybody. No more having a small person finding the seat hard to rotate, or a heavy set person—supposedly physically stronger—finding the seat to easy to rotate, hence, unstable.
In view of the innovative advantages mentioned above, it is the principal object of the present invention to offer a chair mechanism whereby the seat slides over curved surfaces.
It is a further object to provide an armless chair having a reclinable seat.
Yet another object of this invention is to provide greater aesthetics freedom of design, reliability and easy of manufacturing.